我有一个相当复杂的问题。我有一个扩展的gridview控件，我发誓曾经一直工作，但我离开了一段时间，回来了，它不再起作用了（我是唯一的程序员）。
扩展gridview的设计使其始终显示页脚行（用于插入新行）。它正确加载和显示现有数据。如果没有行，则添加数据可以正常工作。但是如果我在已经有现有行的gridview中添加一个新行，我就会遇到gvPhones.FooterRow为null的问题，因此无法找到我正在引用的控件。
这是扩展的gridview类（从stackoverflow页面获得）：
using System.Linq;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.ComponentModel;
//https://stackoverflow.com/questions/994895/always-show-footertemplate-even-no-data/10891744#10891744
namespace WebForms.LocalCodeLibrary.Controls
{
//modified from https://stackoverflow.com/questions/3437581/show-gridview-footer-on-empty-grid
public class GridViewExtended : GridView
{
private GridViewRow _footerRow;
[DefaultValue(false), Category("Appearance"), Description("Include the footer when the table is empty")]
public bool ShowFooterWhenEmpty { get; set; }
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), Browsable(false)]
public override GridViewRow FooterRow
{
get
{
if ((this._footerRow == null))
{
this.EnsureChildControls();
}
return this._footerRow;
}
}
protected override int CreateChildControls(System.Collections.IEnumerable dataSource, bool dataBinding)
{
//creates all the rows that would normally be created when instantiating the grid
int returnVal = base.CreateChildControls(dataSource, dataBinding);
//if no rows were created (i.e. returnVal == 0), and we need to show the footer row, then we need to create and bind the footer row.
if (returnVal == 0 && this.ShowFooterWhenEmpty)
{
Table table = this.Controls.OfType<Table>().First<Table>();
DataControlField[] dcf = new DataControlField[this.Columns.Count];
this.Columns.CopyTo(dcf, 0);
//creates the footer row
this._footerRow = this.CreateRow(-1, -1, DataControlRowType.Footer, DataControlRowState.Normal, dataBinding, null, dcf, table.Rows, null);
if (!this.ShowFooter)
{
_footerRow.Visible = false;
}
}
return returnVal;
}
private GridViewRow CreateRow(int rowIndex, int dataSourceIndex, DataControlRowType rowType, DataControlRowState rowState, bool dataBind, object dataItem, DataControlField[] fields, TableRowCollection rows, PagedDataSource pagedDataSource)
{
GridViewRow row = this.CreateRow(rowIndex, dataSourceIndex, rowType, rowState);
GridViewRowEventArgs e = new GridViewRowEventArgs(row);
if ((rowType != DataControlRowType.Pager))
{
this.InitializeRow(row, fields);
}
else
{
this.InitializePager(row, fields.Length, pagedDataSource);
}
//if the row has data, sets the data item
if (dataBind)
{
row.DataItem = dataItem;
}
//Raises the RowCreated event
this.OnRowCreated(e);
//adds the row to the gridview's row collection
rows.Add(row);
//explicitly binds the data item to the row, including the footer row and raises the RowDataBound event.
if (dataBind)
{
row.DataBind();
this.OnRowDataBound(e);
row.DataItem = null;
}
return row;
}
}
}
以下是ASPX页面中的相关内容：
<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="ContactEdit.aspx.cs" Inherits="WebForms.Directory.ContactEdit" %>
<%@ Register TagPrefix="gcctl" Namespace="WebForms.LocalCodeLibrary.Controls" Assembly="WebForms" %>
<asp:Content ID="Content1" ContentPlaceHolderID="Head" runat="server">
<style>
</style>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
<div id="bodycontent" class="body-content">
<h2><asp:Literal ID="formheader" runat="server" /></h2>
<!-- Start: Main Customer section -->
<asp:Panel ID="mainformcontent" runat="server" CssClass="formsection">
<section id="mainform" class="simplelayoutform">
<asp:TextBox id="customerid" type="hidden" runat="server" />
<asp:TextBox id="contactid" type="hidden" runat="server" />
</section>
</asp:Panel>
<!-- End: Main Customer section -->
<!-- Start: Phones section -->
<asp:SqlDataSource ID="gvPhonesDataSource" runat="server" OnInserted="gvPhonesDataSource_Inserted"
ConnectionString="<%$ ConnectionStrings:ConnString %>"
SelectCommand="SELECT p.[CustomerPhoneID]
,p.[CustomerID]
,LTRIM(COALESCE(cc.FirstName,'') + ' ' + COALESCE(cc.LastName,'')) AS ContactFullName
,p.CustomerContactID
,p.PhoneTypeID
,lp.PhoneType
,p.[PhoneNumber]
,p.[Extension]
,p.[FormattedPhone]
,p.[IsActive]
,CASE WHEN p.LocationID IS NULL THEN CASE WHEN p.CustomerContactID IS NULL THEN 0 ELSE 1 END ELSE 2 END AS SortOrder
FROM [dbo].[Phones] p
LEFT JOIN dbo.Contacts cc ON p.CustomerContactID = cc.CustomerContactID
LEFT JOIN list.PhoneTypes lp ON p.PhoneTypeID = lp.PhoneTypeID
WHERE p.CustomerContactID = @CustomerContactID"
DeleteCommand="DELETE FROM [dbo].[Phones] WHERE [CustomerPhoneID] = @CustomerPhoneID"
InsertCommand="INSERT INTO [dbo].[Phones] ([CustomerID]
, [CustomerContactID]
, [PhoneNumber]
, [Extension]
, [PhoneTypeID]
, LastModifiedByStaffID)
VALUES (@CustomerID
, @CustomerContactID
, CASE WHEN COALESCE(@FormattedPhone, '')='' THEN NULL ELSE LTRIM(RTRIM(LEFT(dbo.RemoveNonNumeric(@FormattedPhone),10))) END
, CASE WHEN COALESCE(@FormattedPhone, '')='' THEN NULL ELSE CASE WHEN LTRIM(RTRIM(SUBSTRING(dbo.RemoveNonNumeric(@FormattedPhone),11,1000))) = '' THEN NULL ELSE LTRIM(RTRIM(SUBSTRING(dbo.RemoveNonNumeric(@FormattedPhone),11,1000))) END END
, @PhoneTypeID
, @StaffID)"
UpdateCommand="UPDATE [dbo].[CustomerPhones]
SET [CustomerContactID] = @CustomerContactID
, [PhoneNumber] = CASE WHEN COALESCE(@FormattedPhone, '')='' THEN NULL ELSE LTRIM(RTRIM(LEFT(dbo.RemoveNonNumeric(@FormattedPhone),10))) END
, [Extension] = CASE WHEN COALESCE(@FormattedPhone, '')='' THEN NULL ELSE CASE WHEN LTRIM(RTRIM(SUBSTRING(dbo.RemoveNonNumeric(@FormattedPhone),11,1000))) = '' THEN NULL ELSE LTRIM(RTRIM(SUBSTRING(dbo.RemoveNonNumeric(@FormattedPhone),11,1000))) END END
, [PhoneTypeID] = @PhoneTypeID
, [IsActive] = @IsActive
, [DateModified] = getdate()
, [LastModifiedByStaffID] = @StaffID
WHERE [CustomerPhoneID] = @CustomerPhoneID">
<SelectParameters>
<asp:ControlParameter Name="CustomerContactID" Type="Int32" ControlID="contactid" PropertyName="Text" />
</SelectParameters>
<DeleteParameters>
<asp:Parameter Name="CustomerPhoneID" Type="Int32" />
</DeleteParameters>
<UpdateParameters>
<asp:ControlParameter Name="CustomerContactID" Type="Int32" ControlID="contactid" PropertyName="Text" />
<asp:Parameter Name="FormattedPhone" Type="String" />
<asp:Parameter Name="PhoneTypeID" Type="Int32" />
<asp:Parameter Name="IsActive" Type="Boolean" />
<asp:SessionParameter Name="StaffID" Type="Int32" SessionField="StaffID" />
<asp:Parameter Name="CustomerPhoneID" Type="Int32" />
</UpdateParameters>
<InsertParameters>
<asp:ControlParameter Name="CustomerID" Type="Int32" ControlID="customerid" PropertyName="Text" />
<asp:ControlParameter Name="CustomerContactID" Type="Int32" ControlID="contactid" PropertyName="Text" />
<asp:Parameter Name="PhoneTypeID" Type="Int32" />
<asp:Parameter Name="FormattedPhone" Type="String" />
<asp:SessionParameter Name="StaffID" Type="Int32" SessionField="StaffID" />
</InsertParameters>
</asp:SqlDataSource>
<asp:Panel ID="phonesformcontent" runat="server" CssClass="formsection separate">
<section id="phonesform" class="simplelayoutform">
<h3>All Phones</h3>
<gcctl:MyCheckBox ID="chkPhoneShowInactive" Text="Show Inactive?" Checked="false" AutoPostBack="true" OnCheckedChanged="chkPhoneShowInactive_CheckedChanged" runat="server" />
<asp:label id="lblPhoneMessage" CssClass="responsemsg" runat="server" enableviewstate="False" />
<gcctl:gridviewextended ID="gvPhones" runat="server" DataSourceID="gvPhonesDataSource"
AutoGenerateColumns="False" DataKeyNames="CustomerPhoneID" EmptyDataText="No phones on record."
CssClass="searchresultsgrid" ShowFooter="True" OnRowCommand="gvPhones_RowCommand" AllowSorting="True"
ShowFooterWhenEmpty="true" OnRowDataBound="gvPhones_RowDataBound">
<Columns>
<asp:BoundField DataField="CustomerPhoneID" InsertVisible="false" ReadOnly="true" Visible="False" />
<asp:TemplateField HeaderText="Phone Type" SortExpression="PhoneType">
<FooterTemplate>
<asp:DropDownList ID="cboPhoneTypeID" runat="server"
DataSourceID="DataSourcePhoneTypes" DataTextField="PhoneType" DataValueField="PhoneTypeID"
SelectedValue='<%# Bind("PhoneTypeID") %>'>
</asp:DropDownList>
</FooterTemplate>
<EditItemTemplate>
<asp:DropDownList ID="cboPhoneTypeID" runat="server"
DataSourceID="DataSourcePhoneTypes" DataTextField="PhoneType" DataValueField="PhoneTypeID"
SelectedValue='<%# Bind("PhoneTypeID") %>'>
</asp:DropDownList>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="lblPhoneTypeID" runat="server" Text='<%# Bind("PhoneType") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Phone" SortExpression="PhoneNumber">
<FooterTemplate>
<asp:TextBox runat="server" Text='<%# Bind("FormattedPhone") %>' ID="txtPhone"></asp:TextBox>
</FooterTemplate>
<EditItemTemplate>
<asp:TextBox runat="server" Text='<%# Bind("FormattedPhone") %>' ID="txtPhone"></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label runat="server" Text='<%# Bind("FormattedPhone") %>' ID="lblPhone"></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Active?" SortExpression="IsActive">
<FooterTemplate>
<asp:CheckBox runat="server" Checked='<%# Bind("IsActive") %>' ID="chkPhoneIsActive"></asp:CheckBox>
</FooterTemplate>
<EditItemTemplate>
<asp:CheckBox runat="server" Checked='<%# Bind("IsActive") %>' ID="chkPhoneIsActive"></asp:CheckBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label runat="server" Text='<%# Bind("IsActive") %>' ID="lblPhoneIsActive"></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField ShowHeader="False">
<EditItemTemplate>
<asp:LinkButton runat="server" Text="Update" CommandName="Update" CausesValidation="True" ID="PhoneUpdate"></asp:LinkButton> <asp:LinkButton runat="server" Text="Cancel" CommandName="Cancel" CausesValidation="False" ID="PhoneEditCancel"></asp:LinkButton>
</EditItemTemplate>
<ItemTemplate>
<asp:LinkButton runat="server" Text="Edit" CommandName="Edit" CausesValidation="False" ID="PhoneEdit"></asp:LinkButton> <asp:LinkButton runat="server" Text="Delete" CommandName="Delete" CausesValidation="False" ID="PhoneDelete"></asp:LinkButton>
</ItemTemplate>
<FooterTemplate>
<asp:LinkButton runat="server" Text="Save New Phone" CommandName="FooterInsert" CausesValidation="True" ID="PhoneInsert"></asp:LinkButton>
</FooterTemplate>
</asp:TemplateField>
</Columns>
</gcctl:gridviewextended>
<div id="phonenotes" class="tip">
<div>NUMBERS ONLY - NO LETTER CODES IN THE PHONE FIELD!</div>
<div>Be sure to always enter the area code, especially if you're also adding an extension.</div>
<div>Note that only numbers will stay in the "Phone" field. Anything else you enter will disappear once it goes behind the scenes. The first 10 digits will become the phone number, and any remaining digits will become the extension.</div>
</div>
</section>
</asp:Panel>
<!-- End: Phones section -->
<div id="responsetextdiv" class="error"><asp:Literal ID="responsetext" runat="server"></asp:Literal></div>
</div>
<asp:XmlDataSource ID="DataSourcePhoneTypes" runat="server" DataFile="~/XML/PhoneTypes.xml" EnableCaching="true">
</asp:XmlDataSource>
</asp:Content>
以下是我收到错误的代码：
protected void gvPhones_RowCommand(object sender, GridViewCommandEventArgs e)
{
// Insert data if the CommandName == "Insert"
// and the validation controls indicate valid data...
if (e.CommandName == "FooterInsert" && Page.IsValid)
{
//ERROR HAPPENS ON THE FOLLOWING LINE:
DropDownList PhoneTypeID = (DropDownList)gvPhones.FooterRow.FindControl("cboPhoneTypeID");
TextBox FormattedPhone = (TextBox)gvPhones.FooterRow.FindControl("txtPhone");
gvPhonesDataSource.InsertParameters["PhoneTypeID"].DefaultValue = PhoneTypeID.SelectedValue.ToString();
string sFormattedPhone = null;
if (!string.IsNullOrEmpty(FormattedPhone.Text))
sFormattedPhone = FormattedPhone.Text;
gvPhonesDataSource.InsertParameters["FormattedPhone"].DefaultValue = sFormattedPhone;
gvPhonesDataSource.InsertParameters["CustomerID"].DefaultValue = customerid.Text.ToString();
gvPhonesDataSource.InsertParameters["CustomerContactID"].DefaultValue = contactid.Text.ToString();
gvPhonesDataSource.InsertParameters["StaffID"].DefaultValue = System.Web.HttpContext.Current.Session["StaffID"].ToString();
// Insert new record
gvPhonesDataSource.Insert();
}
}
我得到的完整错误是：
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
Source Error:
Line 276: if (e.CommandName == "FooterInsert" && Page.IsValid)
Line 277: {
Line 278: DropDownList PhoneTypeID = (DropDownList)gvPhones.FooterRow.FindControl("cboPhoneTypeID");
Line 279: TextBox FormattedPhone = (TextBox)gvPhones.FooterRow.FindControl("txtPhone");
Line 280:
Source File: <snip> Line: 278
Stack Trace:
[NullReferenceException: Object reference not set to an instance of an object.]
GCWebForms.Directory.ContactEdit.gvPhones_RowCommand(Object sender, GridViewCommandEventArgs e) in <snip>ContactEdit.aspx.cs:278
System.Web.UI.WebControls.GridView.OnRowCommand(GridViewCommandEventArgs e) +137
System.Web.UI.WebControls.GridView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +95
System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +49
System.Web.UI.WebControls.GridViewRow.OnBubbleEvent(Object source, EventArgs e) +146
System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +49
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5450
当单步执行时（当尝试向已经包含数据的gridview添加新行时），我发现gvPhones.FooterRow表示它为null。同样，只有在gvPhones中有数据时才会发生这种情况。如果数据表为空，则脚注插入代码可以正常工作。
任何帮助将不胜感激！ ： - ）
编辑：在Page_Load后面添加相关代码。我刚刚添加了DataBind（）语句，但它没有什么区别。
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
bool bolNewRec = (this.iContactID == null);
phonesformcontent.Visible = (!bolNewRec);
if (bolNewRec)
{ //snipping unrelated code
}
else
{
//snipping code that loads the data into the page
gvPhones.Sort("SortOrder, PhoneType", SortDirection.Ascending);
}
}
if (phonesformcontent.Visible)
gvPhones.DataBind();
}
...而且，以防万一，这里是RowDataBound：
protected void gvPhones_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
DataRowView rowView = (DataRowView)e.Row.DataItem;
bool bolShowInactive = chkPhoneShowInactive.Checked;
if (!bolShowInactive && (Convert.ToBoolean(rowView["IsActive"]) == false))
e.Row.Visible = false;
else
e.Row.Visible = true;
rowView = null;
}
if (e.Row.RowType == DataControlRowType.Footer)
{
CheckBox chkIsActive = (CheckBox)e.Row.FindControl("chkPhoneIsActive");
chkIsActive.Checked = true;
chkIsActive = null;
}
}
答案 0 :(得分：1)
尝试在代码中使用发件人，如下所示：
替换此行：
DropDownList PhoneTypeID = (DropDownList)gvPhones.FooterRow.FindControl("cboPhoneTypeID");
为此：
DropDownList PhoneTypeID = (DropDownList)((GridView)sender).FooterRow.FindControl("cboPhoneTypeID");
另外，如果问题不在回发中，请检查页面加载。
我的回答是基于这个问题： Unable to get gridview footer values in RowCommand
<强>更新
更改GridViewExtended类，
ShowFooterWhenEmpty属性：
[Category("Behavior")]
[Themeable(true)]
[Bindable(BindableSupport.No)]
public bool ShowFooterWhenEmpty
{
get
{
if (this.ViewState["ShowFooterWhenEmpty"] == null)
{
this.ViewState["ShowFooterWhenEmpty"] = false;
}
return (bool)this.ViewState["ShowFooterWhenEmpty"];
}
set
{
this.ViewState["ShowFooterWhenEmpty"] = value;
}
}
<强> GridViewRow ：
private GridViewRow _footerRow;
public override GridViewRow FooterRow
{
get
{
GridViewRow f = base.FooterRow;
if (f != null)
return f;
else
return _footerRow;
}
}
我根据此链接进行了更改： Always show FooterTemplate, even no data
答案 1 :(得分：0)
我最后整理了整个班级。相反，我制作了常规的asp：gridviews，这些数据源基于数据源，在关键列中有一行带-1的联合选择（因为我的所有表都有单个自动增量PK，没有行在键列中合法地具有-1） ，然后将以下内容放在RowDataBound中：
if (e.Row.RowType == DataControlRowType.DataRow)
{
DataRowView rowView = (DataRowView)e.Row.DataItem;
string sKeyName = gvPhones.DataKeyNames[0].ToString();
if ((rowView[sKeyName].ToString() == "-1"))
e.Row.Visible = false;
else
e.Row.Visible = true;
rowView = null;
}
这会隐藏键列中包含-1的任何行。因此，gridview中始终至少有一行（即使隐藏了一行），并且页脚行始终显示。